src/libpng/pngwio.c

   1
   2 /* pngwio.c - functions for data output
   3  *
   4  * Last changed in libpng 1.2.37 [June 4, 2009]
   5  * For conditions of distribution and use, see copyright notice in png.h
   6  * Copyright (c) 1998-2009 Glenn Randers-Pehrson
   7  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
   8  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
   9  *
  10  * This file provides a location for all output.  Users who need
  11  * special handling are expected to write functions that have the same
  12  * arguments as these and perform similar functions, but that possibly
  13  * use different output methods.  Note that you shouldn't change these
  14  * functions, but rather write replacement functions and then change
  15  * them at run time with png_set_write_fn(...).
  16  */
  17
  18 #define PNG_INTERNAL
  19 #include "png.h"
  20 #ifdef PNG_WRITE_SUPPORTED
  21
  22 /* Write the data to whatever output you are using.  The default routine
  23  * writes to a file pointer.  Note that this routine sometimes gets called
  24  * with very small lengths, so you should implement some kind of simple
  25  * buffering if you are using unbuffered writes.  This should never be asked
  26  * to write more than 64K on a 16 bit machine.
  27  */
  28
  29 void /* PRIVATE */
  30 png_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  31 {
  32    if (png_ptr->write_data_fn != NULL )
  33       (*(png_ptr->write_data_fn))(png_ptr, data, length);
  34    else
  35       png_error(png_ptr, "Call to NULL write function");
  36 }
  37
  38 #if !defined(PNG_NO_STDIO)
  39 /* This is the function that does the actual writing of data.  If you are
  40  * not writing to a standard C stream, you should create a replacement
  41  * write_data function and use it at run time with png_set_write_fn(), rather
  42  * than changing the library.
  43  */
  44 #ifndef USE_FAR_KEYWORD
  45 void PNGAPI
  46 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  47 {
  48    png_uint_32 check;
  49
  50    if (png_ptr == NULL)
  51       return;
  52 #if defined(_WIN32_WCE)
  53    if ( !WriteFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
  54       check = 0;
  55 #else
  56    check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
  57 #endif
  58    if (check != length)
  59       png_error(png_ptr, "Write Error");
  60 }
  61 #else
  62 /* This is the model-independent version. Since the standard I/O library
  63  * can't handle far buffers in the medium and small models, we have to copy
  64  * the data.
  65  */
  66
  67 #define NEAR_BUF_SIZE 1024
  68 #define MIN(a,b) (a <= b ? a : b)
  69
  70 void PNGAPI
  71 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  72 {
  73    png_uint_32 check;
  74    png_byte *near_data;  /* Needs to be "png_byte *" instead of "png_bytep" */
  75    png_FILE_p io_ptr;
  76
  77    if (png_ptr == NULL)
  78       return;
  79    /* Check if data really is near. If so, use usual code. */
  80    near_data = (png_byte *)CVT_PTR_NOCHECK(data);
  81    io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);
  82    if ((png_bytep)near_data == data)
  83    {
  84 #if defined(_WIN32_WCE)
  85       if ( !WriteFile(io_ptr, near_data, length, &check, NULL) )
  86          check = 0;
  87 #else
  88       check = fwrite(near_data, 1, length, io_ptr);
  89 #endif
  90    }
  91    else
  92    {
  93       png_byte buf[NEAR_BUF_SIZE];
  94       png_size_t written, remaining, err;
  95       check = 0;
  96       remaining = length;
  97       do
  98       {
  99          written = MIN(NEAR_BUF_SIZE, remaining);
 100          png_memcpy(buf, data, written); /* Copy far buffer to near buffer */
 101 #if defined(_WIN32_WCE)
 102          if ( !WriteFile(io_ptr, buf, written, &err, NULL) )
 103             err = 0;
 104 #else
 105          err = fwrite(buf, 1, written, io_ptr);
 106 #endif
 107          if (err != written)
 108             break;
 109
 110          else
 111             check += err;
 112
 113          data += written;
 114          remaining -= written;
 115       }
 116       while (remaining != 0);
 117    }
 118    if (check != length)
 119       png_error(png_ptr, "Write Error");
 120 }
 121
 122 #endif
 123 #endif
 124
 125 /* This function is called to output any data pending writing (normally
 126  * to disk).  After png_flush is called, there should be no data pending
 127  * writing in any buffers.
 128  */
 129 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
 130 void /* PRIVATE */
 131 png_flush(png_structp png_ptr)
 132 {
 133    if (png_ptr->output_flush_fn != NULL)
 134       (*(png_ptr->output_flush_fn))(png_ptr);
 135 }
 136
 137 #if !defined(PNG_NO_STDIO)
 138 void PNGAPI
 139 png_default_flush(png_structp png_ptr)
 140 {
 141 #if !defined(_WIN32_WCE)
 142    png_FILE_p io_ptr;
 143 #endif
 144    if (png_ptr == NULL)
 145       return;
 146 #if !defined(_WIN32_WCE)
 147    io_ptr = (png_FILE_p)CVT_PTR((png_ptr->io_ptr));
 148    fflush(io_ptr);
 149 #endif
 150 }
 151 #endif
 152 #endif
 153
 154 /* This function allows the application to supply new output functions for
 155  * libpng if standard C streams aren't being used.
 156  *
 157  * This function takes as its arguments:
 158  * png_ptr       - pointer to a png output data structure
 159  * io_ptr        - pointer to user supplied structure containing info about
 160  *                 the output functions.  May be NULL.
 161  * write_data_fn - pointer to a new output function that takes as its
 162  *                 arguments a pointer to a png_struct, a pointer to
 163  *                 data to be written, and a 32-bit unsigned int that is
 164  *                 the number of bytes to be written.  The new write
 165  *                 function should call png_error(png_ptr, "Error msg")
 166  *                 to exit and output any fatal error messages.  May be
 167  *                 NULL, in which case libpng's default function will
 168  *                 be used.
 169  * flush_data_fn - pointer to a new flush function that takes as its
 170  *                 arguments a pointer to a png_struct.  After a call to
 171  *                 the flush function, there should be no data in any buffers
 172  *                 or pending transmission.  If the output method doesn't do
 173  *                 any buffering of ouput, a function prototype must still be
 174  *                 supplied although it doesn't have to do anything.  If
 175  *                 PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
 176  *                 time, output_flush_fn will be ignored, although it must be
 177  *                 supplied for compatibility.  May be NULL, in which case
 178  *                 libpng's default function will be used, if
 179  *                 PNG_WRITE_FLUSH_SUPPORTED is defined.  This is not
 180  *                 a good idea if io_ptr does not point to a standard
 181  *                 *FILE structure.
 182  */
 183 void PNGAPI
 184 png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
 185    png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
 186 {
 187    if (png_ptr == NULL)
 188       return;
 189
 190    png_ptr->io_ptr = io_ptr;
 191
 192 #if !defined(PNG_NO_STDIO)
 193    if (write_data_fn != NULL)
 194       png_ptr->write_data_fn = write_data_fn;
 195
 196    else
 197       png_ptr->write_data_fn = png_default_write_data;
 198 #else
 199    png_ptr->write_data_fn = write_data_fn;
 200 #endif
 201
 202 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
 203 #if !defined(PNG_NO_STDIO)
 204    if (output_flush_fn != NULL)
 205       png_ptr->output_flush_fn = output_flush_fn;
 206
 207    else
 208       png_ptr->output_flush_fn = png_default_flush;
 209 #else
 210    png_ptr->output_flush_fn = output_flush_fn;
 211 #endif
 212 #endif /* PNG_WRITE_FLUSH_SUPPORTED */
 213
 214    /* It is an error to read while writing a png file */
 215    if (png_ptr->read_data_fn != NULL)
 216    {
 217       png_ptr->read_data_fn = NULL;
 218       png_warning(png_ptr,
 219          "Attempted to set both read_data_fn and write_data_fn in");
 220       png_warning(png_ptr,
 221          "the same structure.  Resetting read_data_fn to NULL.");
 222    }
 223 }
 224
 225 #if defined(USE_FAR_KEYWORD)
 226 #if defined(_MSC_VER)
 227 void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
 228 {
 229    void *near_ptr;
 230    void FAR *far_ptr;
 231    FP_OFF(near_ptr) = FP_OFF(ptr);
 232    far_ptr = (void FAR *)near_ptr;
 233
 234    if (check != 0)
 235       if (FP_SEG(ptr) != FP_SEG(far_ptr))
 236          png_error(png_ptr, "segment lost in conversion");
 237
 238    return(near_ptr);
 239 }
 240 #  else
 241 void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
 242 {
 243    void *near_ptr;
 244    void FAR *far_ptr;
 245    near_ptr = (void FAR *)ptr;
 246    far_ptr = (void FAR *)near_ptr;
 247
 248    if (check != 0)
 249       if (far_ptr != ptr)
 250          png_error(png_ptr, "segment lost in conversion");
 251
 252    return(near_ptr);
 253 }
 254 #   endif
 255 #   endif
 256 #endif /* PNG_WRITE_SUPPORTED */